Meibomian Gland Dysfunction (MGD)

What is Meibomian Gland Dysfunction

Meibomian gland dysfunction (MGD) is a chronic, diffuse abnormality of the meibomian glands — the oil glands of the eyelids — marked by blockage of their openings and/or changes in the quality and quantity of their secretion. These glands produce meibum, the oily outer layer of the tear film that keeps tears from evaporating. When the glands are obstructed or inflamed, the lipid layer becomes deficient, tears evaporate too quickly, and the ocular surface becomes unstable and inflamed. MGD is the single most common cause of evaporative dry eye disease.

The Meibomian Glands

The meibomian glands are large sebaceous (oil) glands embedded vertically within the tarsal plate of each eyelid — roughly 25–40 in the upper lid and 20–30 in the lower lid. Their openings sit in a single row along the lid margin, just behind the lash line. With every blink, the glands release a thin film of meibum that spreads across the eye to form the outermost lipid layer of the tear film. This oily layer slows evaporation and gives the tear film a smooth optical surface.

• Obstruction: Thickened oil and keratin plug the gland openings, so meibum cannot reach the tear film.
• Gland dropout (atrophy): Chronic obstruction causes the glands to shrink and disappear — visible on meibography and often irreversible, which is why early treatment matters.

Causes & Risk Factors

MGD is usually multifactorial. Common contributors include:

• Aging — gland function declines and dropout increases with age
• Ocular rosacea — strongly associated; lid-margin telangiectasia and inflammation are typical
• Posterior blepharitis — inflammation centered on the gland orifices
• Demodex mite infestation of the lashes and glands
• Reduced or incomplete blinking — prolonged screen and reading time
• Contact-lens wear
• Hormonal changes (androgen deficiency, menopause) and some medications (isotretinoin, antihistamines)
• Systemic conditions — Sjögren’s syndrome, graft-versus-host disease, and other inflammatory disease

Symptoms

MGD often produces the same symptoms as dry eye, frequently worse toward the end of the day or after screen use:

• Dryness, grittiness, or a foreign-body sensation
• Burning, stinging, or eyelid heaviness
• Intermittent blurred vision that clears with blinking
• Redness and crusting or oily debris along the lid margin
• Recurrent styes (hordeola) or chalazia from blocked glands
• Paradoxical watering — reflex tearing triggered by an unstable, evaporating tear film

Diagnosis & Evaluation

Diagnosis is clinical, based on a focused slit-lamp examination of the eyelid margins supported by specialized tests:

• Lid-margin exam — capped or plugged gland orifices, telangiectasia, thickening, and notching
• Gland expression — gentle pressure assesses whether meibum is clear, cloudy, granular, or absent
• Tear break-up time (TBUT) — shortened in evaporative dry eye
• Meibography — infrared imaging that shows gland structure and the degree of dropout
• Adjuncts — tear osmolarity, lipid-layer interferometry, and ocular-surface staining

Treatment

MGD is managed in a stepwise fashion, escalating with severity. Consistency matters more than any single therapy.